Aging of trivalent metal hydroxide/oxide gels in divalent metal salt solutions: Mechanism of formation of layered double hydroxides (LDHs)

Abstract

While the aging of freshly precipitated Al(OH)3 gels in solutions of Mg and Ni salts leads to LDH formation at high (> 12) pH, aging of 'Fe(OH)3' leads to LDH formation in Mg salt solutions but not in Ni salt solutions. 'Cr(OH)3' gels do not form LDHs on aging in any of the divalent metal salts. In general, conditions that promote the re-dissolution of the trivalent hydroxide also promote LDH formation showing that oxoanionic species such as AlO2- have a role in LDH formation.